Respiratory mask frame



FIG. 1 is a front perspective view of a respiratory mask frame according to our design;

FIG. 2 is a reverse perspective view thereof;

FIG. 3 is a front view thereof;

FIG. 4 is a rear view thereof;

FIG. 5 is a top view thereof;

FIG. 6 is a bottom view thereof;

FIG. 7 is a right side view thereof; and,

FIG. 8 is a left side view thereof. 

The ornamental design for a respiratory mask frame, as shown. 